The present invention relates to a memory expansion device for use in increasing the ROM and adding RAM to a program cartridge. The program cartridge is used in association with electronic video games. The present invention relates to various electronic circuitry, including certain logic elements and ROM and RAM, allowing expansion of the memory without increasing or changing the number of conductor contact ribbons formed in parallel for interfacing the cartridge directly to the bus connector of the electronic video game.
The basic art to which the present invention relates is only a few years old. The video games using program cartridges are commercially available, and have been mass marketed at an astonishing rate.
Many television connected microprocessor systems, for use as video games or educational systems, are designed to accept programs from interchangeable cartridges. A program is stored in the ROM of each cartridge. The number of memory addresses available in the cartridges is limited by the number of contact ribbons used in interfacing the cartridge to the video game base unit, and in some cases, the video game base unit does not provide a control line to utilize RAM in a cartridge, so no enable write signal can be interfaced with the cartridge electronic circuit elements. The present invention overcomes these problems of increasing the memory size and adding RAM without modifing the base unit or the bus connector of the base unit.